Process of cleaning metal articles



Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE HARRY P. COB-SON, 01: LAKEWOOD, AND RALPH E. LAWRENCE, OF WICKLIFFE. OHIO.

ASSIGNORS TO THE GBASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A COR- PORATION OF DELAWARE PROCESS OF CLEANING METAL ARTICLES No Drawing.

This invention relates to processes of cleaning metals by the use of acids in which a substance is added to the cleaning bath which inhibits the action of the acid upon the metal and relates particularly to a type of inhibiting substances which were found to be exceedingly efficient.

It has already been proposed to use as inhibitors sulfonation products of high boiling petroleum fractions or sludge acids from petroleum refining operations, but we found that such inhibitors have only a very moderate efliciency when compared with the inhibitors of our present invention.

It is well known that the careful and low temperature carbonization of certain oil shales produces sulfur containing distillates which have properties entirely different from those of ordinary mineral oils. Treatments of the sulfur containing fraction of these oils with concentrated sulfuric acid or oleum produce sulfonic acids which are more or less water soluble. The ammonium salts of these sulfonic acids have found application in the treatment of skin diseases and for various industrial uses. They are known and listed in the pharmaceutical literature as ichthyol or ichthyol sulfonates. The chemical constitution of these ichthyol products is imperfectly known. They contain in dessicated form, where they appear as dark colored viscous oils. or ungu-ents, in the neighborhood of 10% sulfur, part of which is supposed to be in the form of sulfones and thiophenes and they have a marked but not unpleasant, terpenic or ester like odor, entirely difi'erent from that of mineral oil products. Synthetic ichthyols have been produced by treatment of mineral oils with sulfur at temperatures of around 200 C. and subsequent sulfonation as well as by the sulfurization of sulfonated mineral oils. These synthetic ichthyols, while not in every instance of the same therapeutical efliciency as natural ichth yol products, are of the same general properties and of a similar chemical constitution, as far as ascertainable, as natural ichthyols, both types of compounds have in common that they are sulfonation products of mineral oils, and that they contain in the neighborhood of 10% sul- Serial No. 398,556.

fur which is, according to present knowledge, contained in the compounds partly in the form of sulfones and possibly also in the form of thiophenes.

We have now found that these natural and synthetic ichthyol type products have to a very marked degree the property of inhibiting the action ofwcidlslyppen metals while they do not, 1n any mar 8t gree affect the dissolution by the acid of oxides, salt, scale, rust or other undesirable incrustation and corrosion products associated with the metals which are submitted to acid treatments.

Such acid cleaning treatments are extensively used in the steel industry where they are commonly known as pickling operations and require tremendous amounts of acids. i

There are. however, many other processes in which acids could be used to dissolve rust or incrustations upon metals. If no provision is made to check the action of the acid upon the metal itself an attack of it takes places with evolution of hydrogen and as such attack is entirely irregular and weakens the article, such acid treatment becomes only pract-ical where an inhibitor can be used conjointly with the acid. The use of inhibitors has opened a new and continuously increasing field for acid metal cleaning processes and our new inhibitors are useful in pickling operations as well as in the other acid metal cleaning processes. I

It has recently been shown that the inhibitors exercise their action upon the hydrogen ion of a non-oxidizing acid bath and is entirely independent of the anion of the acid. This is confirmed by our tests. where we found that our new inhibitors displav their beneficial action in various dilute. non-oxidizing acids, such as sulfuric, hydrochloric, acetic, etc., acids or solution of acid sulfates. etc. I

The application of our invention to pickling and acid metal cleaning operations does not involve any material change in these operations exceptthe addition of the inhibitor to the bath and it will be found that such additlon produces beneficial results in the various processes and under the various conditions of concentration, temperature, kind of acid used, which involve the removal by acids of undesirable incrustation on metallic articles. 5 The amount of our inhibitors needed to produce a useful protection of the metal in such cleaning operations is usually not more than of 1% based on the weight of the bath and in many instances considerably less than this amount will already produce the beneficial effect.

Typical representatives of our novel inhibitors which have been used by us as inhibitors are, for instance, the following:

Natural ichthyol which is a brownish black viscous mass. It contained about 33% water determined as loss in drying, about 9.3 total sulfur based on dry weight, had a characteristic, not unpleasant odor and was the amzlnonium salt of oil shale distillate sulfonic aci s.

Synthetic ichthyol which is an aqueous solution of sulfurized sulfonates of mineral oils. The solution was a dark brown liquid of an odor similar to that of natural ichthyol. It contained about 15.7% sulfur based on dry weight and was about a 33% solution of the sulfonates.

Small amounts of these products when added to the commonly used 6% sulfuric acid pickling baths or other similar cleaning baths, produced a much better ickled stock or cleaner metal than in the a sence of the inhibitor.

The ei'licienc of these inhibitors can be determined in lalioratory tests by measurement of the hydrogen evolved from a piece of steel immersed under comparative conditions in dilute, for instance, 34% sulfuric acid, without and with the addition of varying amounts of the inhibitor, or by determining the loss of weight of a clean metal strip immersed in a dilute acid.

For the gas evolution test, pieces of black sheetwere immersed for various periods of time at room temperature in a 34% sulfuric acid containing 0.1, 0.05 and 0.005% of the inhibitor respectively. The inhibitor was first added to concentrated acid and this diluted with water to the desired strength. Using the above natural ichthyol there was practically no evolution of gas even after 20 hours immersion of black mild steel sheet of about 8 square inches surface and in the case of the synthetic ichthyol only a few cc of gas were obtained, whereas in a blank test there were more than 350 cc. gas evolved already after 6 hours immersion.

In comparing the loss of weight of samples of metal treated in acids as commonly used in pickling and cleaning operations we immersed for instance, samples of black sheet steel of 24 square inches surface for one hour in 6% sulfuric acid at 150 F. and determined the weight before and after the test. These conditions approximate common steel pickling operations. We found that samples immersed in acids containing from 0.03 to 0.06% by weight of dessicated natural or synthetic ichthyol lost only between 4 and 6% of the loss shown by similar samples treated under identical conditions but in the absence of an inhibitor. In other words, the efiiciency of our novel inhibitors is about 96 to 94%.

It is common practice in many pickling formulaa to add salt or foam producing agents to the bath. Such compounds can be added directly to ichthyols, and we obtain in this manner dry or pasty products which are conveniently handled in commerce as well as in the pickling room.

These compounded inhibitors are then added in the requisite amounts to any desired pickling and cleaning bath.

We claim:

1. In a process of pickling and cleaning metal articles which comprises subjecting said articles to an acid bath containing asthe active pickling and cleaning ingredient a non-oxidizing acid, the step of inhibiting the action of said acid upon the metal by the incorporation into said acid of an inhibitor comprising a sulfonation product of a mineral oil which contains in the neighborhood of 10% or more total sulfur and which contains part of said sulfur in the form of sulfones and which in its general properties is identical with or similar to ichthyol.

2. In a process of pickling and cleaning metal articles which comprises subjecting said articles to an acid bath containing as the active pickling and cleaning ingredient a non-oxidizing acid, the step of inhibiting the action of said acid upon the metal by the incorporation into said acid of an inhibitor comprising a water soluble, sulfurized, sulfonated mineral oil containing in the neighborhood of 10% or more total sulfur.

3. In a process of pickling and cleaning metal articles which comprises subjecting said articles to an acid bath containing as the active pickling and cleaning ingredient a non-oxidizing acid, the step of inhibiting the action of said acid upon the metal by the incorporation into said acid of an inhibitor comprising a synthetic ichthyol product.

4. composition of matter for pickling and cleaning metal articles comprising a dilute, non-oxidizing acid and a small amount of an inhibitor, comprising sulfurized, sulfonated mineral oil containing in the neighborhood of 10% or more total sulfur.

5. A composition of matter for pickling and cleaning metal articles comprising a dilute, non-oxidizing acid and a small amount of an inhibitor comprising a sulfonation product of a mineral oil, which contains in the neighborhood of 10% or more total sulfur and which contains part of said sulfur in the form of sulfones and which in its gen- 40.4. bUIVHUSI IUNS,

eral properties is identical with or similar to ichthyol.

6. A composition of matter comprising as its active acid inhibiting ingredient. an inhibitor which is chemically a sulfonation product of a mineral oil, which contains in the neighborhood of 10%v or more total sulfur and which contains part of said sulfur in the form of sulfon cs and which in its general properties is identical with or similar to ichthyol.

In testimony whereof, we afiix our signatures.

HARRY P. CORSON. RALPH E. LAWREXCE. 

